The present invention relates to an extendable joint for piping to be embedded or spanned such as those for sending oil, wind, vapor, hot water or the like.
In the piping to be embedded or spanned as described above, generally a bellows type of extendable pipe joint is installed for accommodating extension or contraction generated in the axial direction due to change in temperature.
In the case as described above, however, a thrust force which is proportional to a product of an effective cross section of the bellows and a pressure is generated, and it is required to provide an anchor on the piping to accommodate a sum of the thrust force and that required for contraction. In addition, a valve set on the piping must be removed from the piping each time the piping is serviced periodically or replaced with new one.
In the piping as described above, when a bore of the piping is large or a high pressure is loaded to the piping, the work for setting an anchor is very difficult because of the thrust force, which causes increase in the construction cost, and when the valve is removed, even if bolt nuts connecting the valve to the piping are removed, it is difficult to remove the valve, so that the piping must be displaced in the axial direction, so that a large scale and hard work is required to achieve the object.
An object of the present invention is to provide an extendable joint which can solve the problems relating to the conventional embedded or spanned piping as described above, and also which does not require a large-scale and difficult work for setting a work, not cause cost increase due to difficulty in removing the valve.
To achieve the object as described above, the present invention provides an extendable pipe joint, wherein the cylindrical body thereof comprises first and second external cylinders removably connected to each other; a first pressure-balancing cylinder is set in the first external cylinder; a second pressure-balancing cylinder is set in the second external cylinder so that the second pressure-balancing cylinder can be moved with a coupling lever in the axial direction; the first and second pressure-balancing cylinders have first and second pressure-balancing plates opposite to each other and are coupled to each other with a first bellows; the second pressure-balancing cylinder and second external cylinder are coupled to each other with a second bellows; nozzles are formed on peripheral walls of the first and second pressure-balancing cylinders; and opening sections of the first and second pressure-balancing cylinders are communicated to the piping respectively.
Further in the present invention, an air hole communicating a space between the first pressure-balancing plate and the second pressure-balancing plate to outside is provided on the peripheral wall of the first pressure-balancing cylinder, and in the invention of Claim 3, inside of the second bellows is communicated to the outside at the opening section of the second external cylinder. In the invention of Claim 4, a drain exhaust is formed in the second external cylinder.